Astrophysical Constraints on the Symmetry Energy and the Neutron Skin of ²⁰⁸Pb with Minimal Modeling Assumptions

Journal Article · 02 November 2021 · Physical Review Letters

DOI: https://doi.org/10.1103/physrevlett.127.192701 · OSTI ID:1832376

Essick, Reed  ^[1]; Tews, Ingo  ^[2]; Landry, Philippe  ^[3]; Schwenk, Achim  ^[4]

---

1. Perimeter Inst. for Theoretical Physics, Waterloo, ON (Canada); Univ. of Chicago, IL (United States)
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
3. California State Univ. (CalState), Fullerton, CA (United States)
4. Technische Univ. Darmstadt (Germany); GSI-Helmholtzzentrum fur Schwerionenforschung, Darmstadt (Germany); Max Planck Inst. fuer Kernphysik, Heidelberg (Germany)

The symmetry energy and its density dependence are crucial inputs for many nuclear physics and astrophysics applications, as they determine properties ranging from the neutron-skin thickness of nuclei to the crust thickness and the radius of neutron stars. Recently, PREX-II reported a value of 0.283 ± 0.071 fm for the neutron-skin thickness of ²⁰⁸Pb, implying a slope parameter L = 106 ± 37 MeV, larger than most ranges obtained from microscopic calculations and other nuclear experiments. We use a nonparametric equation of state representation based on Gaussian processes to constrain the symmetry energy S₀, L, and $$R^{^{208}Pb}_{skin}$$ directly from observations of neutron stars with minimal modeling assumptions. The resulting astrophysical constraints from heavy pulsar masses, LIGO/Virgo, and NICER clearly favor smaller values of the neutron skin and L, as well as negative symmetry incompressibilities. Finally, combining astrophysical data with PREX-II and chiral effective field theory constraints yields S₀ = $$33.0^{+2.0}_{-1.8}$$ MeV , L = $$53^{+14}_{-15}$$ MeV, and $$R^{^{208}Pb}_{skin} = 0.17^{+0.04}_{-0.04}$$ fm.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR); National Science Foundation (NSF); German Research Foundation (DFG); USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: 89233218CNA000001; AC02-05CH11231; AC52-06NA25396; 20190617PRD1; 20190021DR; PHY-1836734; OISE-1927130; PHY-0757058; PHY-0823459
• OSTI ID: 1832376
• Report Number(s): LA-UR-21-20527; TRN: US2216732
• Journal Information: Physical Review Letters, Vol. 127, Issue 19; ISSN 0031-9007
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English